From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx4+3HwwTjPHeQMPh8c6w928QNDyscTnR4dEOuWcGxAiE++aaG6WDT0YM2FWV9MBQxNhy0j0D ARC-Seal: i=1; a=rsa-sha256; t=1524406365; cv=none; d=google.com; s=arc-20160816; b=fRxl0pBdT0FP/mJTbrNnMv5C+9o4ExMNRMbqzwLt42JZhT/sAQnweTyoZ+p6AH3J2f ReOdwfRN/Cr+mpgjdRDMtQoAxaVzgJSsXE6Udqru1Tq0319JwG2u+lxcDOdltaHVczrU wUhLk8ApxENQUhZyiWJ4ddwruGwE4P51q46GLlMqQ5z2BkAfEBM61KZFFXnmZ71Qnaxl XW+O2s/ZRo4udBWKOqasqHyumpWFX64aCv6ANFgj5BsTTjLV/Bl5g7losww4VQwTBNVv 2tfJ5DFF8blhSsT69AELUOwywSmvvQQUQUYIRNmNx3L8y2lfYVkwTSHvFYmBWGIwUF/b pgaw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=jsOLuxG1ryBk5LZnadQ7ygc+uFLTBG+qPPwTMZBtm68=; b=mZ+p75Q/bv7wHbN4xKiYabLSSRzAA8WfqpREl4wGhujximpDZb2B08J5FPP52RGHBU sYmgOiJ/FbslPvQdze9gsjO7r7CJAVSFK9OZEkL/DcIPEvFMDfOyeSGIxDueot4U8laJ 8EvLxU3nj3ai1BGV8SwHrAla7sqPuly7fRnPm8VEYGNPXnjmyJOnoXWbI60yNdd8cAqk TN8ZWT6YRZSS7SjNDml90LXPjN042tfBE4BePs7xhgKy8L6JqLcHqcZ/RCdX5J5qfdNG l6VjAkxGlyyyQkofAlJkoApWNNGJpQDxEE5dLCJ6MAMOGd5ukfp48ytbyZ6L4cr64mqn OROw== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Maxime Jayat , Ludovic Desroches , Vinod Koul Subject: [PATCH 4.9 44/95] dmaengine: at_xdmac: fix rare residue corruption Date: Sun, 22 Apr 2018 15:53:13 +0200 Message-Id: <20180422135212.217825317@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180422135210.432103639@linuxfoundation.org> References: <20180422135210.432103639@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1598455126397049965?= X-GMAIL-MSGID: =?utf-8?q?1598455928527425707?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Maxime Jayat commit c5637476bbf9bb86c7f0413b8f4822a73d8d2d07 upstream. Despite the efforts made to correctly read the NDA and CUBC registers, the order in which the registers are read could sometimes lead to an inconsistent state. Re-using the timeline from the comments, this following timing of registers reads could lead to reading NDA with value "@desc2" and CUBC with value "MAX desc1": INITD -------- ------------ |____________________| _______________________ _______________ NDA @desc2 \/ @desc3 _______________________/\_______________ __________ ___________ _______________ CUBC 0 \/ MAX desc1 \/ MAX desc2 __________/\___________/\_______________ | | | | Events:(1)(2) (3)(4) (1) check_nda = @desc2 (2) initd = 1 (3) cur_ubc = MAX desc1 (4) cur_nda = @desc2 This is allowed by the condition ((check_nda == cur_nda) && initd), despite cur_ubc and cur_nda being in the precise state we don't want. This error leads to incorrect residue computation. Fix it by inversing the order in which CUBC and INITD are read. This makes sure that NDA and CUBC are always read together either _before_ INITD goes to 0 or _after_ it is back at 1. The case where NDA is read before INITD is at 0 and CUBC is read after INITD is back at 1 will be rejected by check_nda and cur_nda being different. Fixes: 53398f488821 ("dmaengine: at_xdmac: fix residue corruption") Cc: stable@vger.kernel.org Signed-off-by: Maxime Jayat Acked-by: Ludovic Desroches Signed-off-by: Vinod Koul Signed-off-by: Greg Kroah-Hartman --- drivers/dma/at_xdmac.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/dma/at_xdmac.c +++ b/drivers/dma/at_xdmac.c @@ -1473,10 +1473,10 @@ at_xdmac_tx_status(struct dma_chan *chan for (retry = 0; retry < AT_XDMAC_RESIDUE_MAX_RETRIES; retry++) { check_nda = at_xdmac_chan_read(atchan, AT_XDMAC_CNDA) & 0xfffffffc; rmb(); - initd = !!(at_xdmac_chan_read(atchan, AT_XDMAC_CC) & AT_XDMAC_CC_INITD); - rmb(); cur_ubc = at_xdmac_chan_read(atchan, AT_XDMAC_CUBC); rmb(); + initd = !!(at_xdmac_chan_read(atchan, AT_XDMAC_CC) & AT_XDMAC_CC_INITD); + rmb(); cur_nda = at_xdmac_chan_read(atchan, AT_XDMAC_CNDA) & 0xfffffffc; rmb();